The concept of increased branched-chain amino acid oxidation in the hypercatabolic phase of the post skeletal injury period is being used as a basis for new nutritional therapy for patients. This concept, however, does not have direct observation to support the concept of increased branched-chain amino acid oxidation rates after injury. It is the aim of this project to use three separate techniques to measure the effect skeletal trauma has on the oxidation of these amino acids in the rat, and to try to determine which tissues are most affected. The oxidation of C-l4 labelled leucine, valine and isoleucine will be estimated from collected 14CO2 and the distribution of the labeled amino acids among tissue protein will be determined. The second method will measure the activities of branched-chain amino acid transaminase and alpha-keto dehydrogenase in heart, liver and skeletal muscle. The third method will monitor the urinary excretion of the alpha-keto acid analogues of the branched chain amino acids using gas chromatography. This third method will be tested on human urine, also, to determine its applicability as a monitoring method in man. Each of these techniques will be used to follow the time course of the changes during the hypercatabolic phase and into the recovery period. The data from these studies would provide a base line for judging if nutritional therapy in the hypercatabolic period is effective in altering the catabolic flow of these three essential amino acids.